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Re: BIND and live property value consistency

From: Lisa Dusseault <lisa@osafoundation.org>
Date: Thu, 07 Jul 2005 13:29:51 -0700
To: "Julian Reschke" <julian.reschke@gmx.de>
Cc: "Geoffrey M Clemm" <geoffrey.clemm@us.ibm.com>, webdav <w3c-dist-auth@w3.org>
Message-ID: <op.stj8j1nieochem@lisa.local>

Well I think the MUST is better than nothing, but there's probably other  
alternatives -- a careful SHOULD, or even a more nuanced requirement.

"WebDAV states that the getlastmodified property MAY be udpated when  
changes are made to the resource even if the changes aren't to the  
resource body, and this naturally includes changes to the resource's  
bindings.  Note however that clients might use Last-Modified to  
synchronize changes to resources, so servers MUST ensure that the value is  
updated in order to allow synchronization to be correct.  For example,  
when a binding to a resource with last-modified time T1 is replaced with a  
binding to a resource with last-modified time T2, the server either has to  
ensure that T2>T1 or update it accordingly."


On Thu, 07 Jul 2005 10:23:09 -0700, Julian Reschke <julian.reschke@gmx.de>  

> Lisa Dusseault wrote:
>>   It's too bad about confusing existing clients when 'getlastmodified'   
>> changes on some resource without any body changes (the client may be   
>> completely unaware of bindings changse going on elsewhere), but I  
>> guess  that's a less bad approach than possibly causing synchronization  
>> errors.
>>  To me this seems like a perfect argument for requirements in the BIND   
>> spec, not just implementation advice.  Because of the synchronization   
>> problems clients would have if implementors do it wrong, we should add:
>>  "WebDAV (RFC2518) states that the getlastmodified property value MAY  
>> be  updated when changes are made to the resource even if the changes  
>> aren't  to the resource body.  However, because clients may synchronize  
>> resources  based on the value of this property, and because a binding  
>> to one resource  at URL A may replace another binding at the same  
>> address, this requires a  new getlastmodified date in order to trigger  
>> the client to synchronize  properly.  Thus, the server MUST update the  
>> getlastmodified property value  whenever a new binding is added to an  
>> existing resource as well as when  REBIND is used."
>>  Lisa
> Lisa,
> in this case, MUST is wrong as well. A server may very well be aware of  
> any resource mapped previously to that URI, so it *could* make a better  
> decision.
> Anyway, this is a generic HTTP vs WebDAV issue, so please add it to the  
> RFC2518bis issues list; and let's resolve it there.
> Best regards, Julian

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Received on Thursday, 7 July 2005 20:30:13 UTC

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